Visual Target Selection for Saccadic Eye Movements Natural visual scenes require individual objects to be identified for further processing or to serve as targets for impending movements. Much work in the visual system has shown that competitive mechanisms are involved in the selection of objects of interest and in the filtering out of objects not of interest. Eye movement systems are faced with a similar selection problem since only one eye movement can be made at a time and visual scenes contain many possible targets. My long - term goal is to understand how the brain identifies targets of interest and how or whether this information is passed to motor systems. My objective in this proposal is to determine whether the organization of target selection mechanisms for the saccadic eye movement system, responsible for rapidly realigning the direction of sight, is similar to what appears to be prominent in visual perceptual systems. Specifically, I propose to test three hypotheses; first, that superior colliculus neurons (SC, a structure critically involved in saccadic eye movement generation) show competitive interactions like those seen in visual cortical regions and that these interactions change dynamically as saccade onset approaches (Specific Aim 1). Second, that stimulus-stimulus interactions within the SC are modulated by top-down mechanisms (Specific Aim 2), and third, that neurons within the basal ganglia (a set of structures with direct inhibitory inputs to the SC) contain activity reflecting the process of target selection for saccades (Specific Aim 3). The results of the proposed experiments will provide an important framework for understanding volitional movements of the eyes and perhaps other movement systems as well. In addition, by understanding how higher perceptual processes contribute to the production of volitional movements, we will have a more clear understanding of the root of a number of enigmatic symptoms that are not "purely motor".